A battery cell has been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. One type of battery cell is known as the lithium-ion battery. The lithium-ion battery is rechargeable and can be formed into a wide variety of shapes and sizes so as to efficiently fill available space in electric vehicles. For example, the battery cell may be prismatic in shape to facilitate a stacking of the battery cells. A plurality of individual battery cells can be provided in a battery pack to provide an amount of power sufficient to operate electric vehicles.
Battery cells such as lithium-ion battery cells are known to generate heat during operation and as a result of a charge cycle when recharging. When overheated or otherwise exposed to high-temperature environments, undesirable effects can impact the operation of lithium-ion batteries. Cooling systems are typically employed with lithium-ion battery packs to militate against the undesirable overheating conditions. The cooling systems may include cooling plates or fins sandwiched between individual battery cells within the battery pack. The cooling system may have channels through which a coolant flows in a heat transfer relationship with the battery cells.
The battery cells and the cooling systems are often disposed within repeating frame assemblies that form repeating units of the battery pack. The repeating units are stacked and compressed to form the assembled battery pack. It is generally necessary to compress the battery cells and the cooling system within the battery pack in order to form a sufficient seal for delivery of coolant to the cooling system. The battery cells and the cooling system are typically compressed by compression bolts disposed through the repeating frame assemblies of the battery pack.
The repeating frame assemblies are often formed from plastic in order to minimize a mass of the assembled battery pack. However, the plastic materials employed for the frame cannot generally withstand the loads required for assembly and operation of the battery pack. Thus, metallic compression limiters are typically inserted into the repeating frame assemblies for cooperation with the compression bolts. Common compression limiters are formed from either brass or steel. As particular examples, it is known to use 36000 series brass or 1018 series steel. It is also known to use leaded brass. The metallic compression limiters are often installed in the repeating frame assemblies by heat insertion.
The use of compression limiters maintains a structural integrity of the repeating frame assemblies during the operation of the battery pack. However, the metallic compression limiters are necessarily machined separately from the repeating frame assemblies. A high degree of cleanliness is desirable for the battery pack, and the machined metallic compression limiters can undesirably introduce debris such as metallic flakes into the battery pack during the insertion process. The metallic compression limiters can also oxidize over time, and further contaminate the battery pack. The use of the heat insertion equipment for installation of the metallic compression limiters also adds to a complexity of the battery pack assembly.
There is a continuing need for a prismatic repeating frame assembly for a battery pack that facilitates a compression of the battery pack while maintaining a structural integrity of the repeating frame assembly.